Complexes MCQ Quiz in मराठी - Objective Question with Answer for Complexes - मोफत PDF डाउनलोड करा

Concept:

Coordination number -

• Coordination number is the number of coordinate bonds with which the ligands are bound to central ion.
• Ligand can be unidentate, bidentate and polydentate and ambidentate. 

Oxidation state - 

• Oxidation state also known as the oxidation number of an element is the number of positive or negative charges assigned to that element in a compound.
• It is the number of electrons lost or gained by an atom of that element.

Explanation:

Coordination number of Cr in  K3 [Cr(C2O4)3]

• The oxalate (C₂O₄)^2- is a bidentate ligand. 
• Each oxalate ligand coordinate through two oxygen atoms.
• A total of three oxalate ligands are present in the coordination sphere with the Cr metal ion.
• Therefore, the coordination number of Cr is 6.

Oxidation state of Cr in  K3 [Cr(C2O4)3]

• The overall charge on the complex is zero.
• The Sum of oxidation states of all elements in the complex is equal to 0.
• The charge on each oxalate ion is -2, so, the oxidation state of each oxalate ion is -2.
• Let the oxidation state of Cr is 'x'.

Calculation for the oxidation state of Cr - 

K3 [Cr(C2O4)3]

+3 + x + 3(-2) = 0

x - 3 = 0

x = +3

Therefore, the oxidation state of Cr is +3.

Conclusion:

Therefore, The coordination number and oxidation state of Cr in K3 [Cr(C2O4)3] are respectively 6 and 3

Concept:

Coordination number -

• Coordination number is the number of coordinate bonds with which the ligands are bound to central ion.
• Ligand can be unidentate, bidentate and polydentate and ambidentate. 

Oxidation state - 

• Oxidation state also known as the oxidation number of an element is the number of positive or negative charges assigned to that element in a compound.
• It is the number of electrons lost or gained by an atom of that element.

Explanation:

Coordination number of Cr in  K3 [Cr(C2O4)3]

• The oxalate (C₂O₄)^2- is a bidentate ligand. 
• Each oxalate ligand coordinate through two oxygen atoms.
• A total of three oxalate ligands are present in the coordination sphere with the Cr metal ion.
• Therefore, the coordination number of Cr is 6.

Oxidation state of Cr in  K3 [Cr(C2O4)3]

• The overall charge on the complex is zero.
• The Sum of oxidation states of all elements in the complex is equal to 0.
• The charge on each oxalate ion is -2, so, the oxidation state of each oxalate ion is -2.
• Let the oxidation state of Cr is 'x'.

Calculation for the oxidation state of Cr - 

K3 [Cr(C2O4)3]

+3 + x + 3(-2) = 0

x - 3 = 0

x = +3

Therefore, the oxidation state of Cr is +3.

Conclusion:

Therefore, The coordination number and oxidation state of Cr in K3 [Cr(C2O4)3] are respectively 6 and 3

Concept:

Cis-Trans Isomers are isomers that differ in the arrangement of two ligands in square planar and octahedral geometry.

Cis isomers are isomers where the two ligands are 90 degrees apart from one another in relation to the central molecule. This is because Cis isomers have a bond angle of 90^o, between two same atoms.

Trans isomers are isomers where the two ligands are on opposite sides in a molecule because trans isomers have a bond angle of 180^o, between the two same atoms.

When naming cis or trans isomers, the name begins either with cis or trans, whichever applies, followed by a hyphen and then the name of a molecule.

Cis-trans Isomerism is possible with [Pt(en)₂Cl₂]²⁺

Only square planar and octahedral geometries can have cis or trans isomers.

(Dichloro(ethelyenediamine)platinum (II)) shows only optical isomerism. The other complexes do not show stereoisomerism.

Stereoisomerism, is also called as spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers which shares the same molecular formula, but the bond connections or their order differs.

Concept:

Crystal Field Stabilization Energy -

• It is also abbreviated as CFSE.
• It is the amount of stabilization provided by the splitting of d-orbitals in two levels.
• It is denoted by Δo in the octahedral field and Δt in the tetrahedral field.
• If  Δo > Pairing energy, the complex will be a low spin complex.
• If  Δo  < Pairing energy, the complex will be a high spin complex.

Explanation:

Given that the d4 complex has an electronic configuration as  \(\rm t_{2g}^3, e_g^1\), indicates complex is a high spin.

For high spin complexes,  Δo < Pairing energy.

For a high spin d4 complex splitting is - 

CFSE = [-0.4× 3 + 0.6 × 1] Δo .

= - 0.6 Δo 

Conclusion:

Thus, for a d4 complex has an electronic configuration as  \(\rm t_{2g}^3, e_g^1\),  Δo is always < Pairing energy.

Hence, the correct answer is option 1.

Concept:

Effective Atomic Number (EAN) rule -

• The total no. of electrons present with the central metal atom in a coordination complex is called as the EAN.
• It is also known as the 18e^- rule.

It is calculated by using the formula - ​T

Total electron on central metal = (Z-x) + 2nl, 

where

• Z = atomic no. of metal
• x = oxidation state of metal
• n = number of ligands attached
• L = no. of coordinate bonds formed

Explanation:

The total number of electrons accommodated by Fe in [Fe(CO)₅] is given by the Effective Atomic Number(EAN) rule.

According to the EAN rule, 

Total electron on Fe = (Z-x) + 2nl

where

• Z = atomic no. of Fe
• x = oxidation state of Fe
• n = number of ligands attached
• L = no. of coordinate bonds formed

Oxidation no. of Fe in [Fe(CO)₅] is 0.

Thus, EAN for Fe = (26-0) + 2 × 1 × 5 = 26+10 = 36

Hence, the total number of electrons accommodated by Fe = 36

Conclusion:

The total number of electrons accommodated by Fe in  [Fe(CO)₅] is 36.

Correct answer: 4)

Concept:

• According to Crystal Field Theory, as a ligand approaches the metal ion, the electrons in the d-orbitals and those in the ligand repel each other due to repulsion between like charges.
• Thus the d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals splitting in energy. 
• The d_xy, d_xz and d_yz orbitals all lie between the bond axes.
• These three orbitals will be changed in energy only a little.
• These orbitals are more like non-bonding orbitals.
• These orbitals are sometimes called the "t_2g" set of orbitals.

Explanation:

• d-subshell has five orbitals, i.e. d_x²−y²​,d_z²​,d_xy,​d_xz​ and d_yz​.
• There are two d orbitals that will interact very strongly with these ligands: the dx2−y2, which lies directly on the x and y axes, and the dz2, which lies directly on the z-axis.
• Together, these two metal orbitals and the ligand orbitals that interact with them will form new bonding and antibonding molecular orbitals.
• The dx2−y2 and the dz2 orbitals lie along the bond axes.
• These two orbitals will be raised relatively high in energy.
• These orbitals are like antibonding levels.
• These orbitals are sometimes called the "e_g" set of orbitals. The term "e_g" comes from the mathematics of symmetry.

Conclusion:

Thus, dx2 - y2 and dz2 sets of the d- orbitals are directly oriented towards the ligands in octahedral coordination compounds.

Ferrocene contains two rings each having six \(\pi\)-electrons.

Thus ferrocene has total \(12\) \(\pi\)-electrons.

Concept:

Cis-Trans Isomers are isomers that differ in the arrangement of two ligands in square planar and octahedral geometry.

Cis isomers are isomers where the two ligands are 90 degrees apart from one another in relation to the central molecule. This is because Cis isomers have a bond angle of 90^o, between two same atoms.

Trans isomers are isomers where the two ligands are on opposite sides in a molecule because trans isomers have a bond angle of 180^o, between the two same atoms.

When naming cis or trans isomers, the name begins either with cis or trans, whichever applies, followed by a hyphen and then the name of a molecule.

Cis-trans Isomerism is possible with [Pt(en)₂Cl₂]²⁺

Only square planar and octahedral geometries can have cis or trans isomers.

(Dichloro(ethelyenediamine)platinum (II)) shows only optical isomerism. The other complexes do not show stereoisomerism.

Stereoisomerism, is also called as spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers which shares the same molecular formula, but the bond connections or their order differs.

CONCEPT:

π-Bonded Organometallic Compounds

• π-bonded organometallic compounds involve coordination of metal atoms with π-systems (like alkenes, aromatic rings).
• Ethene (C₂H₄) is a simple π-system with a double bond.
• A compound containing ethene (not ethane, which is fully saturated and has no π-bond) in π-coordination is Zeise’s salt.

EXPLANATION:

• Option 1: Zeise's salt → Contains ethene coordinated to platinum via π-bonding. Correct answer.
• 
• Option 2: Ferrocene → Contains cyclopentadienyl rings, not ethene.
• Option 3: Dibenzene chromium → Contains benzene rings, not ethene.
• 
• Option 4: Tetraethyl tin → σ-bonded, no π-bonding with ethene.
• 

Therefore, the correct answer is: Option 1 — Zeise's salt

CONCEPT:

Uses of Organotin Compounds

• Organotin compounds are chemical compounds based on tin with hydrocarbon substituents.
• They are used in a variety of industrial applications due to their unique chemical properties.

EXPLANATION:

• Organotin compounds have several practical applications:
  • Pesticides: Organotin compounds are effective biocides and are used in agricultural settings to control pests.
  • Preservatives of Wood: They are used to protect wood from fungal and insect attacks, thereby increasing the durability of wooden structures.
  • Polyurethane Foams: Organotin compounds act as catalysts in the production of polyurethane foams, which are used in a wide range of products from furniture to insulation.
• Contrary to some misconceptions, organotin compounds can be toxic and have potential health risks.
• However, their carcinogenicity can depend on the specific compound and exposure levels.

Therefore, the statement that they are not carcinogenic is not universally accurate and requires careful consideration.

Therefore, the correct not uses of organotin compounds include are not carcinogenic.